The present invention relates to a process for the treatment of nonwovens with antimicrobial agents, a process for the preparation of a formulation comprising the antimicrobial agents and the nonwovens treated by this method.
xe2x80x9cNon-wovenxe2x80x9d is a type of fabric that is not spun and woven into a cloth, but instead bonded together. According to the ISO definition it is a manufactured sheet, web, or batt of directionally or randomly orientated fibres, bonded by friction, and/or adhesion.
Nonwoven textiles are widely used in disposable as well as durable goods, such as baby diaper, feminine hygiene, adult incontinence, wipers, bed linings, automotive industries, medical face masks, air and water filtration, home furnishing and geotextiles. Such materials can be fabricated by different techniques, such as spunbonding, melt blown, carded thermal bonding and carded chemical bonding, dry and/or wet laid and needlefelts. Because of the nature of such applications the market is increasingly demanding products with specific properties such as antimicrobial efficacy. Efforts have been made in incorporating antimicrobial active agents in binders which sometimes are used to make nonwovens in processes like carded chemical bonding, dry and wet laid.
Amongst various nonwoven products, materials made by spunbonding and melt blown techniques have some unique properties and are becoming more and more important because of advantages in manufacturing as well as in product properties. Spunbond nonwovens can be made directly from thermoplastic polymers such as polypropylene, polyethylene, polyester and nylon. This process offers lower manufacturing cost, improved processability and performance in the final product such as coverstock for disposable baby diapers, feminine hygiene and adult incontinence. Spunbond nonwovens can also be used as durable products such as geotextiles and roof membranes. Characterised by a large surface area and small pore size, melt blown nonwovens differ from traditional spunbonds in their lower fibre denier and fineness. But similarly, melt blown nonwovens are also manufactured by directly extruding thermoplastic polymers, especially high melt flow polypropylene. Their applications include filtration, feminine hygiene, wipers, face masks and absorbents.
Selected antimicrobial substances can be incorporated into the polymer melt before the extrusion. This method enables the antimicrobials to be built into the nonwovens and to migrate onto the surface. Long lasting antimicrobial efficacy of such type of materials is achieved by the continues migration of the active ingredient to the surface. The disadvantage of such type of incorporation is that the processing temperature for manufacturing melt blown and spunbond nonwovens is usually very high, i.e., up to 300xc2x0 C. At such temperature, the involved antimicrobials, especially organic based antimicrobials can cause problems in volatility as well as thermostability.
It is therefore desirable to find an alternative process in which antimicrobials, preferably organic based antimicrobials, are incorporated in nonwoven materials, preferably those made by spunbond and melt blown processes, without undergoing a high temperature process.
Surprisingly, it was found that this object can be achieved in treating an already-formed nonwoven with a formulation comprising
(a) an antimicrobial agent selected from
(a1) halogeno-o-hydroxydiphenyl compound;
(a2) phenol derivative;
(a3) benzyl compound;
(a4) chlorohexidine and a derivative thereof;
(a5) C12-C14alkylbetaine and C8-C18fatty acid amidoalkylbetaine;
(a6) an amphoteric surfactant;
(a7) trihalocarbanilide;
(a8) quaternary and polyquaternary compound; and
(a9) a thiazole compound; and
(a10) a iodine containing agent;
(a11) a naphthyl derivative;
(b) a solubilizing agent; and optionally
(c) at least one copolymer made from two or more monomers, with at least one monomer having good affinity to the textiles and at least another monomer having affinity to the involved antimicrobial substances.
The nonwovens used for the process of the present invention are preferably prepared by spun bond and melt blown processes or by carded chemical bonding, carded thermal bonding, dry and/or wet laid and needlefelts.
Preferably, the antimicrobial agent (a1) is selected from compounds of the formula 
wherein
X is oxygen, sulfur or xe2x80x94CH2xe2x80x94,
Y is chloro or bromo,
Z is SO2H, NO2 or C1-C4-Alkyl,
r is 0 to 3,
o is 0 to 3,
p is 0 or 1,
m is 0 or 1 and
n is 0 or 1;
and at least one of r or o is xe2x89xa00.
Preferably, in the present process, antimicrobial agents (a1) of formula (1) are used, wherein
X is oxygen, sulfur or xe2x80x94CH2xe2x80x94, and
Y is chloro or bromo,
m is 0,
n is 0 or 1,
o is 1 or 2,
r is 1 to 3 and
p is 0.
Of particular interest as antimicrobial agent (a1) is a compound of formula 
wherein
X is xe2x80x94Oxe2x80x94 or xe2x80x94CH2xe2x80x94;
r is 1 to 3; and
o is 1 or 2, and most preferably a compound of formula 
Preferred phenol derivatives (a2) correspond to formula 
wherein
R1 is hydrogen, hydroxy, C1-C4alkyl, chloro, nitro, phenyl or benzyl,
R2 is hydrogen, hydroxy, C1-C6alkyl or halogen,
R3 is hydrogen, C1-C6alkyl, hydroxy, chloro, nitro or a sulfo group in the form of the alkali metal salts or ammonium salts thereof,
R4 is hydrogen or methyl,
R5 is hydrogen or nitro; and
R6 is hydrogen; or a radical of formula (4a) 
Such compounds are typically chlorophenols (o-, m-, p-chlorophenols), 2,4-dichlorophenol, p-nitrophenol, picric acid, xylenol, p-chloro-m-xylenol, cresols (o-, m-, p-cresols), p-chloro-m-cresol, pyrocatechin, resorcinol, orcinol, 4-n-hexylresorcinol, pyrogallol, phloroglucine, carvacrol, thymol, p-chlorothymol, o-phenylphenol, o-benzylphenol, p-chloro-o-benzylphenol and 4-phenolsulfonic acid.
Typical antimicrobial agents (a3) correspond to the formula 
wherein
R1, R2, R3, R4, R5 are each independently of one another hydrogen or chloro; and
R6 is xe2x80x94OH; or xe2x80x94Oxe2x80x94(CO)xe2x80x94C6H5.
Illustrative examples of compounds of formula (5) are benzyl alcohol, 2,4-, 3,5- or 2,6-dichlorobenzyl alcohol and trichlorobenzyl alcohol.
Antimicrobial agent (a4) is chlorhexidine and salts thereof, for example 1,1xe2x80x2-hexamethylene-bis-(5-(p-chlorophenyl)-biguanide), together with organic and inorganic acids and chlorhexidine derivatives such as their diacetate, digluconate or dihydrochloride compounds.
Antimicrobial agent (a5) is typically C8-C8cocamidopropylbetaine.
Amphoteric surfactants as antimicrobial agents (a6) are suitably C12alkylaminocarboxylic and C1-C3alkanecarboxylic acids such as alkylaminoacetates or alkylaminopropionates.
Typical trihalocarbanilides which are useful as antimicrobial agent (a7) are compounds of the formula 
wherein
Hal is chloro or bromo,
n and m are 1 or 2, and
n+m are 3.
The quaternary and polyquaternary compounds which correspond to antimicrobial agent (a8) are of the formula 
wherein
R6, R7, R8 and R9 are each independently of one another C1-C18alkyl, C1-C18alkoxy or phenyl-lower alkyl, and
Hal is chloro or bromo.
Among these salts, the compound of formula 
wherein
n is an integer from 7 to 17, is very particularly preferred.
A further exemplified compound is cetyl trimethylethyl ammonium bromide.
Of particular interest as antimicrobial agent (a9) is methylchloroisothiazoline.
Iodine containing agents (a10) are for example iodopropyl butyl carbamate.
Preffered antimicrobial agent (a11) is the compound of formula 
The antimicrobial agents which are used in the present process are water-soluble or only sparingly soluble in water. In the present aqueous formulation they may therefore be applied in solubilized, emulsified or dispersed form.
The present aqueous formulation therefore additionally comprises a small amount of an organic solvent, a surfactant, a dispersant, and/or an emulsifier as component (b). This component is useful for solubilization and stabilization of the antimicrobial agents in the present aqueous formulation.
Suitable solubilizing agents are anionic, nonionic or zwitterionic and amphoteric synthetic, surface-active substances.
Suitable anionic surface-active substances are:
sulfates, typically fatty alcohol sulfates, which contain 8 to 18 carbon atoms in the alkyl chain, e.g. sulfated lauryl alcohol;
fatty alcohol ether sulfates, typically the acid esters or the salts thereof of a polyadduct of 2 to 30 mol of ethylene oxide with 1 mol of a C8-C22fatty alcohol;
the alkali metal salts, ammonium salts or amine salts of C8-C20fatty acids, which are termed soaps, typically coconut fatty acid;
alkylamide sulfates;
alkylamine sulfates, typically monoethanolamine lauryl sulfate;
alkylamide ether sulfates;
alkylaryl polyether sulfates;
monoglyceride sulfates;
alkane sulfonates, containing 8 to 20 carbon atoms in the alkyl chain, e.g. dodecyl sulfonate;
alkylamide sulfonates;
alkylaryl sulfonates;
a-olefin sulfonates;
sulfosuccinic acid derivatives, typically alkyl sulfosuccinates, alkyl ether sulfosuccinates or alkyl sulfosuccinamide derivatives;
N-[alkylamidoalkyl]amino acids of formula 
wherein
X is hydrogen, C1-C4alkyl or xe2x80x94COOxe2x88x92M+,
Y is hydrogen or C1-C4alkyl,
Z is: xe2x80x94(CH2)m1xe2x88x921xe2x80x94
m1 is 1 to 5,
n1 is an integer from 6 to 18, and
M is an alkali metal ion or an amine ion;
alkyl ether carboxylates and alkylaryl ether carboxylates of formula (11) CH3xe2x80x94Xxe2x80x94Yxe2x80x94A,
wherein 
R is hydrogen or C1-C4alkyl,
Y is: xe2x80x94(CHCHO)1-50xe2x80x94
m2 is 1 to 6, and
M is an alkali metal cation or an amine cation.
The anionic surfactants used may furthermore be fatty acid methyl taurides, alkylisothionates, fatty acid polypeptide condensates and fatty alcohol phosphoric acid esters. The alkyl radicals in these compounds preferably contain 8 to 24 carbon atoms.
The anionic surfactants are usually obtained in the form of their water-soluble salts, such as the alkali metal, ammonium or amine salts. Typical examples of such salts are lithium, sodium, potassium, ammonium, triethylamine, ethanolamine, diethanolamine or triethanolamine salts. It is preferred to use the sodium or potassium salts or the ammonium-(NR1R2R3) salts, wherein R1, R2 and R3 are each independently of one another hydrogen, C1-C4alkyl or C1-C4hydroxyalkyl.
Very particularly preferred anionic surfactants used for the present process are monoethanolamine lauryl sulfate or the alkali metal salts of fatty alcohol sulfates, preferably the sodium lauryl sulfate or sodium laureth-2 sulfate.
Suitable zwitterionic and amphoteric surfactants are imidazoline carboxylates, alkylamphocarboxy carboxylic acids, alkylamphocarboxylic acids (e.g. lauroamphoglycinate) and N-alkyl-b-aminopropionates or N-alkyl-b-iminodipropionates.
Nonionic surfactants are typically derivatives of the adducts of propylene oxide/ethylene oxide having a molecular weight of 1000 to 15000, fatty alcohol ethoxylates (1-50 EO), alkylphenol polyglycol ethers (1-50 EO), ethoxylated carbohydrates, fatty acid glycol partial esters, typically diethylene glycol monostearate, PEG 5 glyceryl stearate; PEG 15 glyceryl stearate; PEG 25 glyceryl stearate; cetearyl octanoate; fatty acid alkanolamides and fatty acid dialkanolamides, fatty acid alkanolamide ethoxylates and fatty acid amine oxides.
Furthermore, the salts of saturated and unsaturated C8-C22fatty acids may be used as solubilizing agents, either by themselves, in admixture with each other or in admixture with the other surface-active substances cited for component (b). Illustrative examples of these fatty acids are typically capric, lauric, myristic, palmitic, stearic, arachic, behenic, dodecenoic, tetradecenoic, octadecenoic, oleic, eicosanic and erucic acid, as well as the technical mixtures of such acids, typically coconut fatty acid. These acids may be obtained in the form of salts, suitable cations being alkali metal cations such as sodium and potassium cations, metal atoms such as zinc atoms and aluminium atoms or nitrogen-containing organic compounds of sufficient alkalinity, typically amines or ethoxylated amines. These salts can also be prepared in situ.
Furthermore, suitable solubilizing agents are dihydric alcohols, preferably those containing 2 to 6 carbon atoms in the alkylene radical, typically ethylene glycol, 1,2- or 1,3-propanediol, 1,3-, 1,4- or 2,3-butanediol, 1,5-pentanediol and 1,6-hexanediol or monohydric alcohol like methanol; ethanol or propanol; and acetone.
If the antimicrobial agents according to component (a) are applied in dispersed form they are milled with an appropriate dispersant, conveniently using quartz balls and an impeller, to a particle size of 1-2 mm.
Suitable dispersants for the antimicrobial agents in the present process are:
acid esters or their salts of alkylene oxide adducts, typically acid esters or their salts of a polyadduct of 4 to 40 mol of ethylene oxide with 1 mol of a phenol, or phosphated polyadducts of 6 to 30 mol of ethylene oxide with 1 mol of 4-nonylphenol, 1 mol of dinonylphenol or, preferably, with 1 mol of compounds which are prepared by addition of 1 to 3 mol of unsubstituted or substituted styrenes to 1 mol of phenol,
polystyrene sulfonates,
fatty acid taurides,
alkylated diphenyl oxide mono- or disulfonates,
sulfonates of polycarboxylates,
the polyadducts of 1 to 60 mol of ethylene oxide and/or propylene oxide with fatty amines, fatty acids or fatty alcohols, each containing 8 to 22 carbon atoms in the alkyl chain, with alkylphenols containing 4 to 16 carbon atoms in the alkyl chain, or with trihydric to hexahydric alkanols containing 3 to 6 carbon atoms, which polyadducts are converted into an acid ester with an organic dicarboxylic acid or with an inorganic polybasic acid,
ligninsulfonates, and, most preferably,
formaldehyde condensates such as condensates of ligninsulfonates and/or phenol and formaldehyde, condensates of formaldehyde with aromatic sulfonic acids, typically condensates of ditolyl ether sulfonates and formaldehyde, condensates of naphthalenesulfonic acid and/or naphthol- or naphthylaminesulfonic acids with formaldehyde, condensates of phenolsulfonic acids and/or sulfonated dihydroxydiphenylsulfone and phenols or cresols with formaldehyde and/or urea, as well as condensates of diphenyl oxide-disulfonic acid derivatives with formaldehyde.
In the dispersion the concentration of the antimicrobial agent is from 0.001 to 50%, preferably from 2-20% b.w.
The aqueous formulation which is used for the present process may further comprise as component (c) at least one copolymer.
The copolymer (c) preferably is a silicone-ethylene oxide copolymer, a silicone-ethylene oxide-propylene oxide copolymer, a vinyl acetate ethylene copolymer, a copolymer of polyvinyl methyl ether-maleic anhydride or a copolymer which is obtained from a hydrophilic silicone.
Ideally this component helps to bind the antimicrobial agents to the nonwoven substrates and simultaneously acts as a surface finishing agent to improve either the hydrophilic or hydrophobic property of the said nonwoven depending on the desired applications.
If the nonwoven is made by another process than a spun bond or melt blown process, i.e. a carded thermal bonding, carded chemical bonding, dry and/or wet laid and needlefelts such a copolymer alternatively may act as a binder which after subsequent curing process is essential for the formation of the web for the said nonwoven.
A key feature in the selection of the copolymer (c) is that it should have good affinity to the nonwoven substrate as well as to the involved antimicrobial agent(s).
The aqueous formulation of the present invention preferably comprises 0.001 to 50, preferably 2 to 20% b.w. of an antimicrobial agent (a), 1 to 50, preferably 5 to 30% b.w. of a solubilizing agent or dispersant (b); 0 to 50, preferably 1 to 10% b.w. of at least one copolymer (c).
The aqueous formulation of the present invention can be prepared by first optionally mixing the solubilized or dispersed antimicrobial agent with the copolymer (c) and than adding the desired amount of water to obtain the aqueous formulation.
The present aqueous formulation can be in the form of solution, dispersion and/or emulsion which can be sprayed onto the surface of textiles. It is also possible to use other processes such as passing said fiber in a dyeing-like process through an aqueous liquor that contains the present formulation or immersing said fiber into an aqueous liquor.
Preferably, the formulation is water based and free of any organic solvents. The advantage of this feature is that during the subsequent drying process, environmental and toxicological problems involving organic solvents will not arise.
The aqueous formulation may also be prepared in concentrated form, which preferably comprises 5 to 50% b.w. of an antimicrobial agent (a), 10 to 50% b.w. of a solubilizing agent or dispersant (b), and 0 to 50, preferably 10 to 50% b.w. of at least one copolymer (c).
This concentrated liquid formulation can be diluted with water and used for further treatment.
The nonwoven fiber materials which can be treated with the formulation of the present invention are made of polypropylene, polyester, polyethylene and polyamide by spunbonding and/or melt blowing where the processing temperatures (for fiber extrusion) are usually very high, i.e. up to 300xc2x0 C. It is also possible that the nonwovens are made of fiber blends such as those above mentioned and other fibers such as viscose, cellulose acetate, polyacrylonitrile, and neutral fibers.
The process of the present invention provides a method of antimicrobial finishing non-woven materials without the need of undergoing thermal process in which high temperatures are involved. Such a process is advantageous for antimicrobials with certain volatility. Additional advantage of such a process is that it can be combined with other treatment such as binding and hydrophilic or hydrophobic finishing. Therefore nonwovens with multi-functions can be obtained with minimal processing costs.
The process of this invention makes it possible to obtain antimicrobial finished nonwovens having long lasting efficacy. The nonwovens finished by the process of the present invention are advantageous with respect to inhibition of microorganisms, reduction of the risk of contamination, reduction of odor, increase in freshness and improvement in hygienic conditions.
Furthermore, the nonwoven textiles which are treated with the process of the present invention exhibit the desired hydrophilicity or hydrophobicity. Particularly, an improved hydrophilicity is often desirable for a wide range of applications such as in personal care products.
Nonwoven materials which are finished with the process of the present invention are particularly suitable for making disposable hygienic products, such as wipers, diapers, adult incontinence or feminine hygiene products.
In the following Examples, percentages are by weight. The amounts of dye and antimicrobial agent are based on pure substance.